This invention relates to radio transceiver antennas that must be tuned to the radio Frequency (RF) being used, transceivers being very sensitive to antenna performance and Voltage Standby Wave Ratio (VSWR) and with capacity to efficiently radiate the transmitter power output under all conditions. Such antennas are employed universally by Maritime, Aviation, Military and Government services, and by the general public as well, and it is the mobility of the transceiver and its antenna which is the focal point of this invention.
It is the High Frequency (HF) range of radio transmission with which this invention is particularly concerned, although it is to be understood that the tuning concept herein disclosed is equally applicable to other radio frequency ranges as may be required. With respect to the HF range covering 1.6 to 30 MH.sub.z frequencies the size and /or length of the antenna becomes a controlling factor. Assuming that the transceiver is installed on and transported by a moving vehicle, clearance along most highways and roadways is 14 feet, whereas the optimum vertical height of a properly tuned antenna can far exceed said highway or roadway clearance. Therefore, it is an object of this invention to increase and decrease the tuned antenna length (as distinguished from height), without limit with respect to highway and/or roadway vertical clearance.
Heretofore, RF antennas have been tuned by means of loading the same with coils that extend their effective length without extending the height thereof. In practice, individual coils have been employed and installed for each radio frequency to be matched. Or, complicated and expensive Antenna Tuners have been used, but they are bulky extra equipment. It is therefore a general object of this invention to fine tune the antenna per se to any radio frequency within a specified range, and in this disclosure the practical High Frequency HF range from 3.5 to 30 MH.sub.z. In practice, the antenna is center loaded with a coil and contactor that adjustably extends the effective length of the antenna.
It is an object of this invention to provide a remote controlled servo by which the antenna can be adjustably tuned from the transceiver location. And, it is still another object of this invention to provide matching impedance of the antenna by means of a shunt to ground, as will be described.
It is omni tuning of a mobile transceiver antenna which is here of concern, accuracy of adjustment being a prime object, and to this end the center loading coil that characterizes this antenna frequency adjustment is supported with accuracy with respect to the coil pitch and is associated with an axially positioned contactor locked in selected placement by a remotely controlled servo motor. The coil and contactor combination cannot drift from the selected placement by the servo motor and self locking elevator nut combination, as will be described.
The foregoing and various other objects and features of this invention will be apparent and fully understood from the following detailed description of the typical preferred forms and applications thereof, throughout which description reference is made to the accompanying drawings.